Gear comparator



I5 Sheets-Sheet 1 INVENTOR RALPH WIKEN ATTORNEY Sept. 13, 1960 R. WIKENGEAR COMPARATOR Filed Jan. 19, 1959 Sept. 13, 1960 R, W|KEN 2,952,081

GEAR COMPARATOR Filed Jan. 19, 1959 3 Sheets-Sheet 2 INVENTOR RALPHWIKEN www ATTORNEY Sept. 13, 1960 R. wlKENv 2,952,081

GEAR COMPARATOR Filed Jan. 19, 1959 3 Sheets-Sheet 3 INVENTOR RALPHWIKEN ATTORNEY United States Patent 0 GEAR COD/[PARATOR Ralph Wiken,Bayside, Wis., assignor to The Falk Corporation, Milwaukee, Wis., acorporation of Wisconsin.

i Filed Jan. 19, 1959, senNe. 787,644

7 Claims. (Cl. '3S-13) This invention relates to gear comparatorsyandmore particularly resides in a slide, chart for Visually comparing thevariation in total length of tooth contact of an intermeshing pair ofspur involute gears on the one hand, and one the`other hand .anintermeshing pair of helical involute gears; the object being todemonstrate the superiority of helical involute `gears over spurinvolute gears, from the point of View of load carrying capacity, whichis based on minimum total contact length.

Such a chart Will be referred to generically as a comparator forvisually comparing the variation in total length of tooth contact ofhelical involute gearing with the variation of total length of toothcontact of spur involute gearing.

A further object of the present invention is to devise a mechanism foractuating such a chart.

` Other objects and advantages will appear from the description whichfollows.

In the description, reference is made to the accompanying drawings,forming a part hereof, in which there is shown by way of illustrationand not of limitation a certain specific form in Which the machine ofthe present invention may be embodied, and certain possible departurestherefrom.

In the drawings:

Fig. 1 is a plan View of the preferred embodiment of the comparator ofthe present invention.`

Fig. 2 is a lengthwise cross-section of the same, seen as though cutalong the line 2-2 of Fig. 1.

Fig. 3 is a plan View of three layers of the frame, with the cover andall movable parts removed.

Fig. 4 is a plan view of one of the gear sectors.

Fig. 5 is a plan view of the slide.

Fig. 6 is a plan View of the complete comparator, except the cover, butwith the position of the three windows of the cover indicated by heavylines. The slide is pushed in to its limit.

Fig. 7 is the same as 6, but with the slide pulled out slightly.

Fig. 8 is the same as 7, but with 4the slide pulled out somewhatfurther.

Fig. 9 is the same .as 8, but with still further.

Fig. 10 is the same as 9, but with the slide pulled out to the limit. lt

Throughout the description, the same reference numeral is :applied tothe same member or to similar members. f

In gear parlance, especially' when dealing with parallel shaft involutegearing, it is customary to describe certain characteristics of ythegears as they would appear on 4the drafting board, projected upon theplane of rotation: i.e., anyplane normal to the axes of the gears. Thusplanes are frequently referred to as lines, cylinders as circles, andlines as points. Accordingly to avoid confusing circumlocutions, thistechnique will be followed herein when applicable. I

YReferring now to the drawings, more particularly to the slide pulledout Patented Sept. 13, 1960 inafter), parts of the internal mechanismwhich are exposed through three windows 23, 24, and 26 (as will beexplained hereinafter), and the manual push-pull tab 27 which is exposedby a notch 28 in the right-hand edgeoff the cover.

Certain arrows and descriptive printed matter are printed on the cover,as shown in Fig. 1. Also printed on the cover are arcs of foursignificant circles of the two intermeshing gears simulated by theinternal mechanism of the comparator. These circles are, from insideoutward: the root circle 29, the lbase circle 31, pitch circle 32, andthe outside circle 33. These circles are projections of thecorrespondingly named cylinders upon the plane of rotation.

Fig. 2 (which is a lengthwise cross-section of the comparator seen asthough cut along the line 2 2 of Fig. 1) and Fig. 3 (which is a planview of the comparator, with the cover and movable parts removed) showthat the comparator is built upon a four layer structure, col* lectivelyknown as the frame, and consisting of: the cover 20, already described,a thick ller layer 34, a guide layer 36, land a back 37. The base, guidelayer, and back, should be of some thin fairly rigid material, such as afine grained cardboard. The filler layer can be of coarse cardboard. Thecover, the back, and the edge portions of the filler 4layer and guidelayer, define a censubstantially identical.

tral cavity 38, designed to contain the movable parts.

The movable parts consist of an upper gear sector 39, a lower gearsection 41, and a slide 42.

The gear sectors should preferably, but need not be The outline of oneis shown in Fig. 4. Each gear sector, considered as an element of anoperative model, obviously has to have a finite thickness; butrepresents a sector of an infinitely thin crosssection of an involutegear (either spur or helical) in a plane of rotation. To savecircumlocution, in the claims it will be called a thin gear sector.

In the embodiment shown, the gear sectors overlie the slide, and henceat least portions of the sectors should be transparent, so as todisclose through the windows in the cover 20 certain lines marked on theslide, which lines Will be explained later herein. Or the slide couldoverlie the gear sectors, in which event at least the central part ofthe slide should be transparent, so as to disclose through centralwindow 24 the outline of the meshing teeth of the gear sectors.

In the preferred embodiment, the two gear sectors 39 and 41 `are made oftransparent celluloid somewhat thinner than the thick filler layer 34,to give the sectors freedom to rotate. Each gear sector comprises aplurality (five, as shown) of successive involute teeth 43, a tab 44containing a central hole 46 to pivot the sector on rivet 22, and twowings 47. These'wings serve to stiffen the sectors and to present auniform appearance under windows 23 and 26. To take up most of thedifference in thickness of thick filler layer 34 and each gear sector ateach pivot rivet 22, there is provided at leach such rivet a cardboardwasher 48.

Preliminary to discussing slide 42, some definitions will now be given.

In involute gearing the plane of action (i.e., the locus of all pointsof gearatooth contact, and said locus extended) is the imaginary planewhich is tangent to the base cylinders of both gears. Inasmuch as thereare two such tangents, it is important to note which of l ithese two isthe plane of action. It is that one of the heavy lines.

.t `actually takes place;

. Y 3 two` .tangents whichshowsrthepoints of contact as movmotion`proceeds. ,i f

The zone ofr action that `portion of the plane of actionfin whichtoothcontaot actually takes piace.

v ing continuously away from the driving hase vcircleas proleof anytooth ofone gear to where that lineintersects theinvolute `portion ofthe far profile of any tooth of the othergear, `willrernain constant,provided At any given instant, two gear teethwhich are inrmovf ingcontact with leach other` touchA eachotherin a sin- -and so 'long asv`the'line of :action intersects both said involute portions, andkprovided andfiso'iong ask -both suchy intersections liey outside ofthatportion of the line of action intercepted hy the points of tangeneythereof to gle line, known as a li-ne of contact. Although- 'this is-afdifferent line lat each` instant, it can be represented as a sidewisemoving line, rat-her than as a succession yof* lines; The total lengthof tooth contac` is `the sum of the lengths of lines of contact existingatany ,givenV The line of action. is the projection of rthe plano ofaction on the plane of rotation.` n

In referring on cover 20 tothe lengt-l1 ofthe line of action, what ismeant is really, the length of action:

f i.e., the length of that portion yofy the yline of action in.

which ltooth contactr actually takes place: ie., thek projection of,Athe zone of actiony on the plane of rotation.

It willhe referred to `herein as the length of action.

The slidek 42y andjcertain markings thereon are'shoWIl ,i

in Fig. 5. It is preferably of` the -samernatenial and i thicknessas theguideflayer 36;y r49 is a line drawnon the slide to indicate thepositionof the actual line of other markings on, the slide will be discussedlater herein.

n Fig. 6 shows ythe slide 42 and thetwo gear sectors;l 39 :and 4Iassembled on the th-ree layers ofthey fran/1o which were shown in Fig.3. The cover is: not shown in Figs. 6 to l0, but the position of each ofthe three Y windows: 23', 24 and 26 of the cover'is .indicated by y tothelimit; i n y Let us now compare lFigs.` guide layer 36 are parallelto the actual line `of action.

'Edges SZfof slide 42bear thesarne relation Yto'line: 4K9k drawn on theslide as edges 51 of the lguide layer do-to the actual'line of action.Accordingly-when the -slide is in -any of its slid positions'in Icheframe, line k4,9indicates l gthe position of the actual line of action.The portionw n t offthi-s line which is. seen"throughfwindowi49, Le.,the

The slide' is` pushedk in (i.e.,` to the left) i sectors, `and the'jline49Y which is drawn on theslide 42 to represent the line of action. So|nuch'ofline 49 ras', is intercepted by the edges/of this rwindowrepresents the portion intercepted between outside circles 3rd-ofthe -fw Y :two gears, is the-onlyfportionf-on which,gearcontact,`

when Sade, a2 is sus .was left-mest position, as" geen in Fig. 6 itsedges 53 Contact corresponding edges, 54'Vr t of guide layer k36, andthus thesetwo sets of edges cooperate to constituter stopt `meanstoklimtlinear nievenient ofthe slide totheleft.` t ,A

When slide 42 Yis slid ,to `right-most. position, as seenin Fig.y 10,`its edges :56contact corresponding edges the 'twobase circles. A

There will now ber discussed what is seen through lthe three windows24,26, and whatiit represents. i

Asfindicated by the two curved arrows printed on the cover andhy theword Driver which accompanies each of them (see Figil), either of thetwo gear sectorsy y can serve as the driver'in't-he direction of therespec-y tive arrow. rDhus when Itab y27 is pulled, slide 42 causes fupper gear sector 39-to rotate counterclockwise and drive gear sector 41clockwise. 42 causes lower .gear sector 41 toy rotate counterclockwise:and ydrive gear; sector 39 clockwise.

he driving points of contact are' Ilocated on line of action 49.` and`are indicated by thelletter P. Apparent points of,r contactr not solocated and indicated' are not" pointsof contacto'` .L25

action and liesthereon. The conformation of, and the Fig. l shows whatis seen.r Figs'. 6` to 10 show, with 'the cover removed, what ishappening behind the scenes as tab 27 is pulled out, Fig. 6correspondingtto Fig. 1. `In Figs.f6 to l0, the positions of the'threewindowsr arey outlined in heavy black lines, as already mentioned;

A The narrow central window is boundedV by intersect- .y ing arcs of theoutside circles 33 ofk the two gea-r sectors f `39 and 41',1 and,showsthe intermeshing kteeth ofthe two lengthof action.y

Y Whatis seen through narrow centralwindow 24 repi resentsr what takesplacey in ai plane of rotation of Ta z pairy of intermeshinginvolutegema-either, spur or helidrawn on slide 42 (see Fig..y 5),` sweepsuccessively across `this window, representingsuccessive.V lines-ofcontact-pfy i the two gears.Vr

Similarly k,what seenr through upper rectangular win#` dow 23 indicatesdiagrammatieally what takes'place in.

cooperate/to constitutest-op means to limitlinea-r movement of the-slideto ythe rright.

Y The actuation of the slide lwill now be discussed.' See y Fig. 5; Onslide 42at each end of line 49 drawn thereon, there is a prQectingpnSS.Theseftwo proiectin-g g i pins are so llocated on :the slidetjhat when,the slide yis i inits left-most position as shown inFig. 6, one projectyingxpin' S8 has a point contact with the involute portion of the farproileof the left tooth of upper sect-ory 59, f and the other projectingpin 58 hasl a point Contact with the involute portion lofthe far profileof the rig-ht tooth oftrlower sector 41. Them-asthe slide moves throughits successive positions of,Figs.,'6 to :10 and back again',

the twoprojecting pins k58 will move 'alongr `the involutc portions ofthe respective profiles, constraining between, them all theyintermediate teeth. Thus either one ofy the `projections"can, impel thedrive sectorjwhile the' other restrains the-driven'sector; f t y y Oneof the'theoriesr upon which-,the present invention isbased is*A that,whenv rtwo'A involute gearsk 'rotate `intetrmes-hed, the' distance alongtheir line-of' action` fromy where thatlineintersects` rtheinvoluteportion `ofthe far 'thegz'o'nfefof"` action of apair ofinvoiute' helioalgears@ asflinesgl drawn on slide 42, sweep successivelyacross 'this window'representing successive lines of contactof v i thetwo gears. l y l "Spacing in la direction parallel torline 49khetw'eensuccessive 1ines59,`and between successiveflines'tl,is the hasefpitchfofboth'sorts'of gears represented-,.- and the 'angle at which lines 61 areinclined to Vlines 59 is the hase helix angle of the helical gearsrepresented. i n it should `be understood that eachoftheselines 59 to 61drawn on the slide, represents `a line` of contact" `only while,g andrto' the extent that, the drawn line isL withinthe contines vof .its`window. For' obviously there` 4can bey no. contact between .twoteethbeyond the'fwidthf of their ',.gears,` ynor!` before the twoy teeth have.rolled into contact, Lnor'lafter` theyfhave rolled out of contact.vEach ofl windows 26 and23has a widthlequalk to the Vlengtlioffactionand' a lengtheqnal. tothe face width of the gears. y l

inasmuch asi theizone ofraction actually'lies in' a plane `perpendicularto theplanes of'rotation',v its repre,-r

sentation does notI have toA be' located' in' any particular 23 ofthecover 20, and

When tab 27 is pushed, slide place on the comparator with relation tothe location of the representation of the intermeshing gears in theplane of action as seen through central window 24. All that is necessanyis that rectangular windows 26 and 23 be properly oriented with relationto the motion of the slide 42. But, for convenience in comparing the twoalternative portrayals of the zone of action, windows 26 and 23 shouldlie across line 49 from each other perpendicular to line 49, with theirsides aligned with the ends of that portion of line 49 exposed throughcentral window 24. Also each line 59 should be -aligned with a point Pof tooth contact and with the adjacent end (as seen through upper window23) of a line 61.

Consider now the diagrammatic representation of a pair of intermeshinginvolute spur gears afforded by central window 24 and lower window 26,as slide 42 is pulled through its cycle from Fig. 6 to Fig. 10, or ispushed back again. Comparing the successive views through the lowerwindow, it is evident that there are always either one or two lines ofcontact each equal in length to the face Vwidth of the gears, and thatthe minimum total length of tooth contact is only half the maximum.Since the load carrying capacity of a gear must be determined by minimumcontact, spur-gear rating has to be lbased on single tooth contact.

Contrast the diagrammatic representation of a pair of intermeshinginvolute helical gears alforded by central window 24 and upper window23, `as slide 42 as pulled through its cycle from Fig. 6 to Fig. 10, oris pushed back again. Comparing the successive views through the upperwindow, it is evident that the variation between maximum and minimumtotal tooth contact is very slight, and that the minimum is larger thanin the case of comparable spur gears. Thus as between comparable spurgears and helical gears, the latter are deservedly assured of a muchhigher rating.

All of this can, of course, be demonstrated by mathematical calculation.But visual demonstration by the use of the comparator of the presentinvention is much more impressive and hence is more likely to stick inthe memory.

From the -foregoing description it will be seen that the presentinvention constitutes a new and useful comparator for visually comparingthe variation in total length of tooth contact of helical and spurgearing, including new and :useful means for actuating the same.

Now that one embodiment of the invention has been shown and described,it is to be understood that the invention is not to be limited to thespecific use, form, or arrangement of parts herein shown and described.

What is claimed is:

l. 'In a comparator for visually comparing a characteristic of helicalinvolute gearing with the corresponding characteristic of spur involutegearing, the combination comprising: a supporting frame; a pair ofintermeshing involute thin gear sectors; means pivoting each sector onthe frame at the axis of that sector; a slide, constrained by the frameto move linearly with respect to the frame, parallel to the line ofaction of the two sectors; stop means limiting each end of such linearmovement; means to be grasped manually to move the slide from limit tolimit; and means for converting the linear motion of the slide intorotary motion of the two sectors, said converting means comprising: twopins projecting from the slide, the two pins being so located on theslide that one of the pins contacts the involute portion of the farprole of a tooth of one of the sectors at said proiiles intersectionwith the line of action, and the other of the pins vcontacts theinvolute portion of the far profile of the other of the sectors at saidprotiles intersection with the line of action, the teeth selected beingteeth the involute portion of the far profile of each of which, duringthe limited motion of the slide, always intersects the line of actionand at a point outside of that portion of the line of action interceptedby the' points of tangency thereof to the base circles.

2. `In a comparator for visually comparing a characteristic of helicalinvolute gearing with the corresponding characteristic or spur involutegearing, the combination comprising: a supporting frame; a pair ofintermeshing involute thin gear sectors; means pivoting each sector onthe frame at the axis of that sector; a slide, constrained by the frameto move linearly with respect to the frame, parallel to the line ofaction of the two sectors; stop means limiting each en d ofsuch linearmovement; means to be grasped manually to move the slide from limit tolimit; and means for converting the linear motion of the slide intorotary motion of the two sectors, said converting means comprising: twopins projecting from the slide on the line of action, so located andspaced apart that, as the slide moves from limit to limit, one pin willmove along the involute portion of the far prole of one tooth of one ofthe sectors, and the other pin will move along the involute portion ofthe far profile of one tooth of the other sector, constraining betweenthe two pins the intermediate engaging teeth of the two sectors. i

3. In a comparator for visually comparing a characteristic of hel-icalinvolute gearing with the corresponding characteristic of spur involutegearing, the combination comprising: a supporting frame; a pair ofintermeshing involute thin gear sectors; means pivoting each sector onthe frame at the axis of that sector; a slide, constrained by the frameto move linearly with respect to the frame, parallel to the line ofaction of the two sectors; stop means limiting each end of such linearmovement; means to be grasped manually to move the slide from limit tolimit; sector engagement means on said slide adapted to alternately moverst one and then the other of said sectors for simultaneous angularmovement of said sectors.

4. In a comparator for visually comparing a characteristic of helicalinvolute gearing with the corresponding characteristic of spur involutegearing, the combination comprising: a supporting frame; a pair ofintermeshing involute thin gear sectors; means pivoting'each sector onthe frame at the axis of that sector; a slide, constrained by the frameto move linearly with respect to the frame, parallel to the line ofaction of the two sectors; stop means limiting each end of such linearmovement; means to be grasped manually to move the slide from limit tolimit; and means for converting the linear motion of the slide intorotary motion vof the two sectors, characterized by the facts that: atleast a portion of whichever of the slide and the pair of sectorsoverlies the other is transparent; the frame includes a cover whichoverlies the slide and the pair of sectors, and which cover has threewindows overlying the transparent portion to disclose successiveportions of the slide and of the pair of sectors as the slide ismanipulated, and the slide has indicia printed thereon, to successivelyshow through the respective windows to indicate digrammatically featuresof gear meshing which are characteristic of both helical and spurinvolute gears, and features of gear meshing which are characteristic ofeach of said two types of gears alone.

5. A comparator according to claim 4, wherein the pair of sectorsoverlie the slide.

6. A comparator according to claim 4, wherein one window in the coverdiscloses so much of the intermeshing teeth of the two sectors as isintercepted between the Outside circles of the two sectors; and whereinthere is a -line drawn on the slide to represent the line of action ofthe two sectors; and wherein so much of said line as is seen throughsaid window at any stage of the manipulation of the slide representsthat portion of the line of action in which tooth cont-act actuallytakes place; and wherein each of the second and third windows in thecover is rectangular, and each such window has a width parallel to theline of action and equal to the length of secondiand'ithirdwindowsliecnopposite sides,ofthe` ace width of the gears krepresentedbythesectors; and

wherein there are drawn on theslide a rst succession of lines parallelto the sides of the 'second window, which linessuccessively passy acrosssaid second Window widthywise as the slidek is manipulated; and as seenthrough Said window krepresentV the lines'of Contact of fthe? pair of fspur gears represented by two sectors; and wherein there are drawn onthe sli'de af'success-ion'of parallel' lines 1nrclined to the sides ofthe third window which lines suc'- cessively pass across said thirdwindow widthwise as the sliden is manipulated, and as seen through saidwindow represent rthe lines of contact of the pair ofy helical gears'vrrepresented by the two sectors; whereby the comparator visuallydemonstrates thatthe total' lengthof tooth con tact of a pair ofintermeshinghelical'involnte gears varies o lessthan does the totallength of tooth contact of a cornparabley pair of spur involute gearsand that thefmini` mum total length of tooth Contact of `a pair ofinterrneshfr ing helical' involute gears is greater thanthe'minimumtotal lengthof tooth Contact of a comparable pair of spur involutegears. f

7. A `comparator accordingto claim 6; 'wherein the representtonfof the'line of action', with their corresponding sides 'aligned'with the endsoi so much of that porfr tion* of vthe liiie representing the line. ofaction of the two ,l sectors asis seen throughthe 'rst window andwherein the twoscce's'sio'ns`r ofw parallel lines are so located' on thes' slide that ech of the first sucession of' parallel li1'1'es,d.nf` l'lng its exposure through the second window, will be n 'Eaton et al.- fr.. June 10, 1924 `2,470,246 y Heisman May`r1'7,y 1949 21,477,441 Coley- July 26, 1949r 2,692,443' Milligan Oct. 26, 1954 p y OTHER REFERENCESn Text-book: Mechahicsi of Machinery, Harnr& Crane,

Brd'Ed'. (1948), McGnaw-Hill (pages 95-97 only).

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No2,952,081 September l3 1960 l Ralph wiken It is hereby certified thaterror appears in the-printed specification of 'the above lnumberedpatent requiring correction and 'bha-b the said Let-bers i Patent shouldread as corrected below.

line 19,7 for `"one the otherv hand" read on the column 5, lines 28 and29s for "'as. pulled" read column 6, line 5, for "characteristic or"read ff" column 7, line 8, for "represented d represented by the twosectors --o e Column l, other hand f is pulled characteristic o `by twosectors" rea (SEAL) Attest: ERNEST W. SWIDER WXXWX Attesting OfficerARTHUR W. CROCKER Acting Commissioner of Patents

